Red Bull driver Sebastian Vettel of Germany holds up eight fingers after winning his eighth race of the season following his win at the Formula One U.S. Grand Prix auto race at the Circuit of the Americas, Sunday, Nov. 17, 2013, in Austin, Texas. (AP Photo/David J. Phillip)

Red Bull driver Sebastian Vettel of Germany holds up eight fingers after winning his eighth race of the season following his win at the Formula One U.S. Grand Prix auto race at the Circuit of the Americas, Sunday, Nov. 17, 2013, in Austin, Texas. (AP Photo/David J. Phillip)

Red Bull driver Sebastian Vettel of Germany tries on a cowboy had after winning the Formula One U.S. Grand Prix auto race at the Circuit of the Americas, Sunday, Nov. 17, 2013, in Austin, Texas. (AP Photo/David J. Phillip)

But with big changes in engine technology coming in 2014, some are wondering, even hoping, that the German's days of ruthless control over the starting grid and the top of the podium are numbered.

"I think there is no doubt that it could get boring if we're not careful in the same way as when Ferrari and Schumacher were as dominant as Red Bull and Vettel," former three-time Formula One champion Jackie Stewart said last week before Vettel claimed his eighth consecutive victory at the U.S. Grand Prix in Texas.

"No one knows which of these engines will deliver, especially in the first year," Stewart said.

The victory came almost a month after Vettel wrapped up his fourth consecutive world championship. If he wins again this weekend in Brazil, he will tie Schumacher's record of 13 victories in a season and tie the overall F1 record for consecutive victories.

But even Vettel seemed to acknowledge that his days dominating the field could end when F1 makes a dramatic change from the current 2.4-litre V8 engines to a 1.6-litre V6 turbocharged unit.

"We have to remember these days," Vettel told his crew over his car radio as he spun his Red Bull car in doughnuts after his victory in Austin.

"Next year is unknown," Vettel said after the race. "I'm sure we will push very, very hard and I'm sure we will fight a lot to maintain our position, but there's no guarantee that next year will be like this year. With the new regulations coming in, I think nobody really knows where he will stand."

In a sport that relies so heavily on the technology of the car, Vettel seems to get little credit from rival drivers. Many see him as lucky to be sitting in the cockpit of the circuit's superior machine.

"They've done a very good job, very consistent, driver and car. It's been on top form," said Force India's Paul Di Resta.

"I think it will be quite interesting to see how it will change or influence next year on the rule changes," added Sauber driver Esteban Gutierrez. "Hopefully, it will make everything more competitive.

Stewart is was more complimentary of Vettel as a championship driver, crediting Vettel's laser-like focus on the track. But Stewart also noted no other team can match Vettel's car.

"He's also the most mature 26-year-old Formula One driver I've ever seen," Stewart said. "He's a worthy world champion, but he should be thanking God he's got a man called (Adrian) Newey."

Newey is Red Bull's chief technical officer. The brains behind Vettel's car has won constructor's championships with three different teams.

"There's no doubt that he will go down in the history of the sport as the most creative designer. He has provided a vehicle for Vettel, if you like, to have the unfair advantage which we all look to have," Stewart said.

Newey shrugged off a question about whether Red Bull will be the favorite in 2014 to win a fifth consecutive title.

"Reliability is going to be quite an issue for the teams, could well be a deciding factor in the championship. Who knows?" Newey said.

Mercedes technical director Paddy Lowe, whose team entered the final race of the 2013 season fighting to hold on to second place in the constructor's championship, called the upcoming changes "really exciting and a good thing for Formula One."

The technical changes will come at a time when many of the top teams will shuffle drivers.

Vettel's Red Bull teammate and rival Mark Webber is leaving F1 next season and will be replaced by Daniel Ricciardo from Red Bull's sister team Toro Rosso. Kimi Raikkonen leaves Lotus for Ferrari, where he'll be paired with Fernando Alonso, giving Ferrari two former world champion drivers.

Felipe Massa leave Ferrari for Williams. And McLaren, which has seen a dramatic drop off in 2013, replaces Sergio Perez with rookie Kevin Magnussen.

There are plenty of top drivers to challenge Vettel and Red Bull next season if teams get the engines right, Stewart said, noting Raikkonen, Alonso and Mercedes teammates Lewis Hamilton and Nico Rosberg are all capable of taking the world title.

"We've got a covey of very good drivers right now," Stewart said. "The McLaren boys ... McLaren have to come back, they are way off at the moment and haven't really been competitive this season."